package com.wc.alorithm_luogu.P5720;

import java.util.Scanner;

/**
 * @Author congge
 * @Date 2023/4/19 16:51
 * @description https://www.luogu.com.cn/problem/P5720
 * 一尺之棰
 */
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int a = sc.nextInt();

        int ans = 1;

        while (Math.pow(2, ans++) <= a) ;

        System.out.println(--ans);
    }
}
